Electroless copper plating

ABSTRACT

An electroless copper plating solution comprising a source of cupric ions, hydroxyl radicals, formaldehyde or a formaldehyde precursor, preferably paraformaldehyde, and a complexing agent for copper; said solution characterized by the addition of a combination of additives comprising an organic silicon compound and a hydrogen inclusion retarding agent and preferably, the combination of the two with at least one member selected from the group consisting of a formaldehyde addition agent and a Group VIII metal salt of the Periodic Chart of the Elements. Copper plate deposited from a solution of this invention is distinguishable from prior art copper deposits by substantially improved bending or tensile properties and a smoother, more highly reflecting appearance. The electroless copper plating solution is capable of providing a rapid rate of copper deposition dependent upon the selection of the complexing agent and the stability of its chelate with copper without sacrifice in tensile or bending properties of the copper deposit.

United States Patent [72] Inventors Charles R. Shipley,Jr.

Newton; Lucia 1!. Shipley, Newton; Michael Gulla, Newton; Oleh B.Dutkewych, Medfield, all of Mass. [21] App]. No. 752,166 [22] Filed Aug.13, 1968 [45] Patented Oct. 26, 1971 [73] Assignee Shipley Company, Inc.

Newton, Mass.

[54] ELECTROLESS COPPER PLATING 19 Claims, No Drawings 52 us. Cl 106/1,117/47, 117/130, 117/160 [51] Int. Cl C23c 3/02 [50] Field ofScar-ch106/1; l17/130,130E,47 R, 35 S, 213,227,160

[56] References Cited UNITED STATES PATENTS 3,093,509 6/1963 Wein v117/213 3,134,690 5/1964 Eriksson 117/213 Primary Examiner- Lorenzo B.Hayes Attorney- Roberts, Cushman & Grover ABSTRACT: An electrolesscopper plating solution comprising a source of cupric ions, hydroxylradicals, formaldehyde or a formaldehyde precursor, preferablyparaformaldehyde, and a complexing agent for copper; said solutioncharacterized by the addition of a combination of additives comprisingan organic silicon compound and a hydrogen inclusion retarding agent andpreferably, the combination of the two with at least one member selectedfrom the group consisting of a formaldehyde addition agent and a GroupVIII metal salt of the Periodic Chart of the Elements. Copper platedeposited from a solution of this invention is distinguishable fromprior art copper deposits by substantially improved bending or tensileproperties and a smoother, more highly reflecting appearance. Theelectroless copper plating solution is capable of providing a rapid rateof copper deposition dependent upon the selection of the complexingagent and the stability of its chelate with copper without sacrifice intensile or bending properties of the copper deposit.

ELECTROLESS COPPER 'I EIG ,4 herein by reference. Improved propertiesare obtained by the addition of a silicon compound to an electrolesscopper solu- BACKGROUND OF THE INVENTION tion where silicon is believedto be the active agent. A major advantage of this system is that therate of copper deposition m 2.22.13.a":is:2i.:2;22:32:15.3;.ssgitiizzziztt:3 v t m en es to a metaldeposmng composmon and ties is not fully understood but-1s believed tobe due, at least in more Pamcularly, to electroless copper platmg sohmonpart, to a surface effect resulting in deposition of a smoother capableof providing an electroless copper deposit of improved bending ortensile properties and having a g y 10 depotsit ftlewer structuraldefects as will be explained in reflective appearance tfdp serdegoziiion solution capable of providing a copper Descnptlon of theplate having substantially improved tensile or bending proper-Electroless copper deposition refers to the chemical plating ties isdisc! t osed m copendmg U.S. Pat. application Ser. No. of copper overacme Surfacies by chemlca] means m the 752,250 filed concurrentlyherewith. Improved properties are absence of an external electriccurrent. Such processes and obtained by the addition of a formaldehydeaddition a em composmons useful therefor are known and are in substamlaland/or a salt of a Group VIII metal of the Periodic Chart of thecommercial use. They are disclosed in a number of prior art patents, forexample, U.S. Pat. Nos. 2,938,805; 3,011,920; El :121: 55 3:31 2amlxture ofthe twom combination wnh 3,310,430, and 3,383,224.

Known electroless copper deposition solutions generally comprise fouringredients dissolved in water. They are (1) a source of cupric ions,usually a copper salt, such as copper sulfate (2) a reducing agent suchas formaldehyde, or preferably, a formaldehyde precursor such asparaformal- I dehyde (3) hydroxide, generally an alkali metal hydroxideand The Subject invention i an illllnlllvelnent 0V6! that usually sodiumhydroxide, sufficient to provide the required described in theabove-noted 3,310,430 and alkaline solution in which said compositionsare effective, and 3,475,136 and p s an electroless c pp r ut n capable(4) a complexing agent for copper sufi'icient to prevent its ofdepositing an electroless copper plate of improved bending precipitationin alkaline solution. A large number of suitable or tensile properties.The copper solution is characterized by complexing agents are known anddescribed in the abovethe addition of the combination of a siliconcompound and a cited patents, and also in U.S. Pat. Nos. 2,874,072;3,075,856; hydrogen inclusion retarding agent, preferably a cyanide com-3,1 19,709; 3,075,855 and 3,329,512 all incorporated herein pound andpreferably the combination of the two with at least by reference. Knownelectroless copper solutions of the above one member selected from thegroup consisting of a formaltype usually provide a plate which ifmechanically dense and dehyde addition agent and a salt of Group VIIImetal of the strong, is somewhat brittle such that it can withstand onlyPeriodic Chart of the Elements. The addition of the hydrogen limitedbending or thermal stress without fracture. This is not inclusionretarding agent to 'a solution containing an organic a substantialdisadvantage where the electroless plate is of the silicon compoundproduces a synergism resulting in substanorder of inillionths of an inchof thickness and is overplated tially increased tensile or bendingproperties. The further ad- STATEMENT OF THE INVENTION with ductileelectrolytic copper. However, where the entire dition of a formaldehydeaddition agent or a salt of a Group desired thickness, typically 1 to 3mils in an electrical applica VIII metal provides a further substantialimprovement in protion, is provided by electroless plating, limitedductility is a perties, especially where a combination of the two areused. In serious limitation. addition to the above-noted improvement inductility proper- One means of improving bending or tensilecharacteristics ties, electroless copper deposits from the solutions ofthis inof an electroless copper plate is described in U.S. Pat. No. 4vention provide the further advantages of excellent laydown PreferredCopper salt 0.002 mole to saturation 0.02 to 0.12 mole. Formaldehyde...0.05 to 3.5 moles 0.1 to 1 mole.

Minimum necessary to maintain copper in solution.. About 1 to 3 timesthe moles of cupric.

Complexing agent Free hydroxide Suflicient to provide pH 10 or greaterHydrogen inclusion retarding agent.. 1 to 1,000 p.p.m 5 to 500 p.p in

Silicon compound Greater than 1 p.p.m 5 to 250 p.p.m.

Formaldehyde addition agent... To that amount that restrictsdcposition.. 0.1 to times the moles of formaldehyde. GroupVIIImetalsa1t...5to2,500p.p.m H J0to1,000p.p.rn.

Water To lliter ofso1ution............................ To 1 literlsolution.

3,310,430 which discloses the addition to a copper plating properties,excellent solderability, and improved smoothness, solution of a watersoluble compound of cyanide, vanadium, brightness, and overallappearance. molybdenum, niobium, tungsten, arsenic, antimony, bismuth,

rare earths of the actin ium series and rare earths of the lanthanumseries. Certain members of the above group, espe- DESCRIPTION OF THEPREFERRED EMBODIMENTS cially the vanadium compounds, providesignificantly improved bending characteristics. The reason for this isnot fully understood but is stated in the patent that the agents poisonA ypic l l le c pper solution in accordance with the the analyti u fa eso a to promote formation and le of invention will have additives in thefollowing concentration hydrogen gas at the catalytic surface, therebyinhibiting the inranges: clusion of hydrogen in the deposit as it forms.It has been It should be understood thatthe above concentration rangesfound that where a complexing agent or bath formulation is arepreferred, but not critical. Variation in the ranges are used permittingrapid deposition of copper with rapid evolupossible without departingfrom the scope of the invention. In tion of hydrogen gas at the surface,the improved ductility or most cases, additives may be added in anamount up to that bending characteristics are frequently sacrificed orlost. amount that poisons the solution.

An alternative means for improving the tensile properties of In theabove formulations, any water soluble copper salt an electroless copperdeposit while simultaneously improving heretofore used forpreparingelectroless copper deposition brightness and other appearanceproperties as described in solutions may be used. Fog example, thehalides, nitrate,

commonly assigned U.S. Pat. No. 3,475,186 incorporated acetate, sulfateand other organic and inorganic acid salts of copper are generallysuitable as is known in the art. Copper sulfate is preferred.

Suitable complexing agents for the copper ions include Rochelle salts,the sodium salts (mono, di, tri, and tetrasodium salts) ofethylenediaminetetraacetic acid, nitrilotriacetic acid and its alkalimetal salts, triethanolamine, modified ethylenediaminetetraacetic acidssuch as N-hydroxyethylenediaminetriacetate, hydroxyalkylsubstituted-dialkylene triamines such aspentahydroxypropyldiethylenetriamine, sodium salicylate, and sodiumtartrate. Other complexing agent for copper ions are disclosed in U.S.Pat. Nos. 2,996,408; 3,075,855; 3,075,856; and 2,938,805.

The preferred class at complexing agents 531155.: described in U.S. Pat.No. 3,329,512 noted above. They include hydroxyalkyl substitutedtertiary amines corresponding to one of the following structures:

l ROH ROH where R is an alkyl group having from two to four carbonatoms, R is a lower alkylene radical and n is a positive integer.Examples of these complexing agents include tetrahydroxypropyl ethylenediamine, pentahydroxypropyl diethylene triamine, trihydroxypropylaminetriisopropanolamine), trihydroxypropyl hydroxyethyl ethylene diamine,etc. As disclosed in said patent, the aforesaid amines are preferablyused in small amounts in combination with other complexing agents andwith certain polymers dispersed in solution such as cellulose ethers,hydroxyethyl starch, polyvinyl alcohol, polyvinylpyrrolidone, peptones,gelatin, polyamides and polyacrylamides.

The rate of copper deposition is, to some extent, dependent upon theselection of the complexing agent. Complexing agents such aspentahydroxypropyldiethylenetriamine provide a fast rate of copperdeposition, usually in excess of 1.0 mils per hour. Though the coppersolutions of this invention provide copper deposits from solutionscontaining any of the known complexing agents for copper ions, they areparticularly well adapted for copper solutions having complexing agentsthat provide a rapid rate of copper deposition.

The silicon additive is one that is soluble in the copper solution andcomprises the organic silicon compounds disclosed in the above-notedPat. No. 3,475,186. It should be noted that many silicon compounds arenot fully soluble in aqueous alkaline solutions and many are consideredinsoluble. However, the silicon, for purposes of the present invention,is required in solution in parts per million and silicon compoundstermed insoluble in aqueous solution usually are soluble to the extentof a few parts per million and suitable for purposes of the presentinvention. For those silicon compounds considered insoluble in water, itis desirable to dissolve the compound in a solvent, such as alcohol, andadd the solution to the electroless copper solution with agitation toform a dispersion or an emulsion. An excess of the silicon compound willbe required to provide the necessary concentration of silicon compoundin solution.

Exemplary of the silicon compound within the scope of the invention arethe silanes, such as silane itself, disilane, tetramethylsilane,trimethylethylsilane, tetraethylsilane, tetraphenylsilane,dimethyldichlorosilane, etc., and low to intermediate molecular weightpolysiloxanes such as silicone fluids, gums, and resins substituted withmethyl, ethyl, vinyl, penyl, chloro, bromo, methoxy, hydroxy, etc. Othersuitable organic silicon compounds are disclosed in the above-noted U.S.Pat. No. 3,475,186.

The polysiloxanes are the least soluble silicon compounds in basiccopper solution, but are preferred because they provide the greatestincrease in ductility and also enhance appearance by yielding a finergrained, more highly reflecting copper deposit. Of the polysiloxanes,the silicon fluids are most preferred. The solid polysiloxanes arepreferably dissolved in a solvent such as alcohol and added to thecopper solution.

The hydrogen inclusion retarding agent is of the same class disclosed inthe above-noted U.S. Pat. No. 3,310,430 and includes simple and complexcompounds which comprise one or more compounds or cyanide, vanadium,molybdenum, niobium, tungsten, rhenium, arsenic, antimony, bismuth,actinium, lanthanum, rare earths of both the lanthanum and actiniumseries and mixtures of the foregoing.

Preferred are those compounds which consist of or comprise elements ofthe type described which have at least two oxidation states. In thispreferred group are compounds comprising vanadium, niobium, molybdenum,tungsten, rhenium, arsenic, antimony, bismuth, cerium, praseodymium,neodymium, samarium, europium, terbium, uranium, and mixtures of theforegoing. These elements are preferably added to the electroless copperplating baths in a form such that the element is at its most stablevalence state. VAnadium and cyanide compound such as alkali metalcyanides exemplified by sodium cyanide and potassium cyanide asdisclosed in the above-noted U.S. Pat. No. 3,310,430 are the mostpreferred hydrogen inclusion retarding agents. Where cyanide is selectedas the hydrogen inclusion retarding agent, it may appear twice in theformulation dependent upon the selection of the remaining additives.

The hydrogen inclusion retarding agent is added to the bath, preferablyas a soluble salt. For example, molybdenum may be supplied as molybdictrioxide as well as water soluble organic and inorganic acid salts ofmolybdenum, as for example alkali and alkaline earth metal, or ammoniummolybdates. Suitable sources of tungsten, molybdenum, rhenium andarsenic are the oxides of such elements, as well as organic andinorganic acid water soluble salts of such elements, e.g., thetungstates, vanadates, arsenates, and rhenates of the metals of Groupsl-A and II-A of the Periodic Chart of the Elements, and ammonium.Preferred for use are the sodium, potassium, and ammonium salts. Sourcesof antimony, bismuth, lanthanum, actinium, and rare earths are theoxides of such elements and water soluble organic and inorganic acidsalts of such elements, including the sulfates, nitrates, halides,acetates, and the like. The function of the hydrogen inclusion retardingagent is not fully understood, but it is reported that it tends topoison the catalytic surface so as to promote the formation and releaseof hydrogen gas to the catalytic surface on which copper is depositingelectrolessly, thereby inhibiting the inclusion of hydrogen in thedeposit as it forms.

The formaldehyde addition agent for purposes of this invention is onethat may be added to solution in amounts sufficient to undergo reactionwith formaldehyde to form a relatively unstable formaldehyde adduct.Reactions of this nature and formaldehyde, addition agents are wellknown in the art and described in various publications, such asFormaldehyde J. Frederick Walker, Reinhold Publishing Company, ThirdEdition 1964, pages 219 to 221, included herein by reference. Preferredaddition agents are sulfites, bisulfites, and phosphites of a metalcation that does not codeposit with copper and preferably an alkalimetal cation. Preferred formaldehyde addition agents are sodium sulfite,potassium bisulfite and sodium phosphite.

The formaldehyde addition agent and formaldehyde or preferably,paraformaldehyde are reacted with each other to form the adduct prior toaddition to the remaining components of the copper solution.

The Group VIII metal salts include water-soluble inorganic salts ofiron, cobalt, nickel, rutenium, rhodium, palladium, osmium, iridium, andplatinum, salts of iron, nickel and platinum being most preferred andslats of palladium being least preferred due to solution stabilityproblems caused by palladium. Suitable salts include phosphates,nitrates, halides,

and acetates of the above metals. A wetting agent may be added tosolution in accordance with art recognized procedures.

The baths may be used at widely varying temperatures, e.g., at leastroom temperature and preferably up to 140 F. As temperature isincreased, it is customary to find an increase in the rate of plating.Temperature is not highly critical, and within the usual operatingranges, excellent, bright deposits of electroless copper havingexcellent tensile or bending properties are obtained. Preferably, thebath is used without agitation.

In using the-electroless copper solution to plate metal, the surface tobe plated should be catalytically active and free of grease andcontaminating material. Where a nonmetallic surface is to be plated, thesurface area to receive the deposit must first be sensitized to renderit catalytically active as by the well-known treatment with an acidicaqueous solution of stannous chloride followed by treatment with adilute aqueous acidic solution of palladium chloride. Alternatively,extremely good sensitization of nonmetallic surfaces is achieved bycontact with an acidic colloidal formulation formed by the admixture ofstannous chloride and a precious metal chloride, preferably palladiumchloride, the stannous chloride being present in stoichiometric excessbased upon the amount of precious metal chloride.

The invention will be better understood by reference to the followingexamples where all parts were plated using the following procedure:

a. Cut a phenolic substrate to a size of 2 inches X 2 inches.

b. Scrub part clean using an abrasive cleaner.

c. Rinse in cold water.

d. Immerse in a solution of a wetting agent identified as ShipleyConditioner 1159 at room temperature for l to 3 minutes.

e. Rinse in cold water.

f. Immerse in a colloidal stannic acid-palladium catalyst (identified asCuposit Catalyst 6F) maintained at room temperature for i to 5 minutes.

g. Rinse in cold water.

h. Immerse in Cuposit Accelerator 19 or a mild perchloric acid solutionmaintained at room temperature for 3 to 10 minutes.

i. Rinse in cold water.

j. Immerse in electroless copper solution maintained at between 110 and130 F. for a period sufficient to provide a deposit of desired thicknessnot to exceed 3 hours.

k. Dry parts and examine deposit for appearance and ductility. Ductilityis determined by peeling a copper deposit from the substrate and bendingthrough 180 in one direction, creasing at the fold, then returning it toits original position with pressing along the crease to flatten it. Thiscycle constitutes one bend. The procedure is repeated until the samplebreaks at the crease. A sample unable to withstand at least to bend isconsidered brittle.

EXAMPLES l-20 CuS0,-$l-I,0 8.0 g. Paraformaldehyde 7.5 g. NaOH(25%solution by wt.) 50.0 ml. tetrahydroxypropylethylene diamine 12.0 g.triisopropanolamine 2.0 g.

Water to l liter of solution The above formulation, with variousadditives was used to deposit electroless copper. Additive compositionand deposit properties are set forth in the following table:

0 deposit electroless copper.

Additive Deposit Deposit eoncenappearthickness Ductility Ex. No.Additives tratiou ance (in. 10- (bends) 1 Control Poor 0.50 Brittle.;0p.p.m do 0.29 yDo. p.p.m-- 0.37 10 p.p.m..} 0. as Britt 250 p.p.m.Fair 0.87 -56.

6 F13514 200 p.p.m....do 0.34 SF1138 200 p.p.m....do 0.46

20 g./l Poor 0.43 Brittle. 8 d 0.46 Do. 00p.p.m do 0.09 Do. 300 p.p.m.do 0.36 D0. 300 p.p.m. do 0.25 Do.

p.p.m. 300 }Poor 0. 32 10 p.p.m.. 300 p.pm. Poor 0.40 7 p.p.m. 30g. Poor0.44

' 0. 50 p 0 43 I6 ZOO I p.p.m. }(iood 0.40 1. 200 p.p.m. 7p.p.m.Good"... 0.32 1%. 300 p.p m- 200 p.p.m. NaHSO: 20 g.ll Good..." 0.43 2.NaCN 7 p.p.m

(l) F-l-3514 A silicone fluid believed to be adimethylpolysiloxane-ethylene glycol copolymer available from theGeneral Electric Company. X

(2) SF-l 138 A silicone fluid believed to be adimethylpolysiloxane-polyalkyleneoxide copolymer available from theGeneral Electric Company.

In the above examples, a deposit was considered poor if it was dark incolor and powdery. A fair deposit was one lighter in color, thoughpowdery in appearance. A good deposit was one having a fine grainedmetallic copper appearance.

The improvements in tensile or bending properties using the preferredelectroless copper solutions of the present invention are readilyapparent by reference to the above examples. Examples 2 to 12 illustratethe use of a single additive. The only single additives showingobservable improvement in properties are the silicon and vanadiumcompounds. Combination of a silicon compound with a cyanide givesgreater improvement. Significantly greater improvements are obtained bythe combination of a silicon compound, a cyanide compound, and a memberselected from the group of a formaldehyde addition agent and a metalsalt of a Group VIII metal (Examples 19 to 20).

EXAMPLES 21 to 25 CuSo,'5H,0 8.0 g. Formaldehyde 7.5 g. NaOH(25%solution) 50.0 ml. Sodium/potassium tartrate 40.0 g.

Water to 1 liter ofsolution The above formulation, with variousadditives, is used to Additive compositions and deposits properties areset forth in the following table:

Copper solutions of this invention find utility for all purposes forwhich electroless copper solutions have heretofore been used includingboth decorative and industrial applications. They are especially usefulfor the formation of printed circuit boards where the deposits act as aductile conductor and as a ductile connector plated onto the walls ofthroughholes. The formation of a printed circuit board havingthrough-holes is illustrated in the following example.

EXAMPLE 26 a. Sandblast one side of a phenolic substrate leaving thesecond surface smooth.

b. Drill through-holes at desired locations.

c. Silk screen a reverse image of a printed circuit pattern onto theroughened surface of the phenolic substrate using an epoxy resin.

d. Immerse in a colloidal palladium sensitizing solutionmaintainedatroom temperature for a period of five minutes.

e. Immerse in a stripping solution comprising 10 grams of copperchloride, 100 grams of 37 percent hydrochloric acid, and water to oneliter. Maintain solution at room temperature and immerse for 6 minutes.

f. Deposit electroless copper of example 25 with copper depositiontaking place on the walls of the through-holes and on the roughenedsurfaces in the image pattern. No copper deposition takes place on theepoxy resist nor on the smooth surfaces of the plastic laminate.

The mechanism by which copper deposits from the solution of thisinvention differs from that of the above-referenced U.S. Pat. No.3,310,430 where hydrogen inclusion retarding agents alone are used toimprove ductility. Though neither mechanism is fully understood, adifferent mechanism is suggested by the observation that the Group VIIImetal cation codeposits with copper, to some extent, in the absence of ahydrogen inclusion retarding agent but codeposition is lessened when ahydrogen inclusion retarding agent is in solution. This is shown by thefollowing examples:

The copper deposits of the above examples were analyzed. In example 27containing both vanadium and nickel compounds in solution, only 0.00088percent nickel was found in the deposit. Omission of the vanadiumcompound in example 28 results in a copper deposit containing 0.100percent nickel. This indicates that the vanadium somehow retarded thecodeposition of nickel.

It should be understood that various changes may be made in theembodiments described above without departing from the spirit and scopeof the invention as defined by the following claims:

1. In an aqueous eleetroless copper plating solution comprising a sourceof cupric ions, hydroxyl radicals, a source of formaldehyde andsufficient complexing agent to render said cupric ions soluble inalkaline solution, the improvement comprising an additive in thesolution of a combination of an organic silicon compound and a hydrogeninclusion retarding agent, said organic silicon compound and saidhydrogen inclusion retarding agent being present in combined amountsinsufficient to prevent copper deposition and each of said organicsilicon compound and said hydrogen inclusion retarding agent beingpresent in solution in an amount of at least one part per million partsof solution.

2. The copper plating solution of claim 1 containing as an additionaladditive at least one member selected from the group consisting of aformaldehyde addition agent in an amount of at least 01 moles per moleof formaldehyde in solution to that amount that prevents deposition ofcopper and a salt of a Group VIII metal of the Periodic Chart of theElements in an amount of at least five parts per million parts ofsolution, said Group VIII metal salt having an anion noninterferin gwith said solution.

3. In an aqueous electroless copper plating-solution comprising a sourceof cupric ions, hydroxyl radicals, formaldehyde and sufficientcomplexing agent to render said cupric ions soluble in alkalinesolution, the improvement comprising an additive in the solution of anorganic silicon compound, a solution-soluble alkali metal cyanidecompound, and at least one of a formaldehyde addition agent selectedfrom the group of alkali metal sulfites, bisulfites and phosphites andsolution soluble salts of a Group VIII metal selected from the group ofiron, nickel and platinum, said salts of a Group VIII metal having ananion noninterfering with said electroless copper solution, said organicsilicon compound and said alkali metal cyanide being present in solutionin combined amount insufficient to prevent copper deposition, each ofsaid organic silicon compound and said alkali metal cyanide beingpresent in solution in an amount of at least one part per million partsof solution, said formaldehyde addition agent being in an amount ofabout 0.1 moles per mole of formaldehyde to that amount that preventscopper deposition and said Group VIII metal salt being present in anamount of at least five parts per million parts of solution.

4. The copper plating solution of claim 3 having as additives thesilicon compound, the cyanide compound, the formaldehyde addition agentand the Group VIII metal salt.

5. The copper solution of claim 4 where the silicon compound is asilicone fluid.

6. The copper solution of claim 5 where the Group VIII metal salt isselected from the group consisting of NiSO,, Fe (SO )X and H PtCl 7. Thecopper solution of claim 3 where the formaldehyde addition agent isselected from the group' consisting of Na,so,, NaI-ISO and Na I-IPO'5H,O.

8. The copper solution of claim 5 where the cyanide compound is sodiumcyanide.

9. In an aqueous electroless copper plating solution comprising a sourceof cupric ions, hydroxyl radicals, a source of formaldehyde andsufficient complexing agent to render said cupric ions soluble inalkaline solution, the improvement comprising an additive in thesolution of a combination of an organic silicon compound and a hydrogeninclusion retarding agent selected from the group consisting of a watersoluble cyanide compound, vanadium, molybdenum, niobium, tungsten,rhenium, arsenic, antimony, bismuth, rare earths of the actinum series,rare earths of the lanthanum series and mixtures of the foregoing, saidorganic silicon compound and said hydrogen inclusion retarding agentbeing present in a combined amount insufficient to prevent copperdeposition and said organic silicon compound and said hydrogen inclusionretarding agent being present in solution in an amount of at least lpartper million parts of solution.

10. The copper plating solution of claim 9 containing as an additionaladditive at least one member selected from the group consisting of aformaldehyde addition agent in an amount of at least 0.1 moles per moleof formaldehyde in solution to that amount that prevents copperdeposition and a salt of a Group VIII metal of the Periodic Chart of theElements in an amount of at least five parts per million parts ofsolution, said formaldehyde addition agent being selected from the groupconsisting of metal salts of a member selected from the group consistingof sulfites, bisulfites and phosphites, and said salt of a Group VIIImetal being selected from the group consisting of salts of platnium,iron and nickel and having an anion noninterfering with said electrolesscopper plating solution.

11. The copper solution of claim 10 having as additives, the

copper salt 0.02 to 0.12 rnoles formaldehyde 0.1 to 1 moles complexingagent i to 3 times the moles of cupric ion free hydroxide 0.] to 03moles hydrogen inclusion 5 to 250 ppm retarding agent silicon compound 5to 250 ppm.

fonnaldehyde addition 0.] to 1 times the moles agent formaldehyde GroupVIII metal salt 30 to 1,000 ppm.

Water to 1 liter ofsolution 15. The copper solution of claim 10 wherethe organic-silicon compound is selected from the group consisting ofsilanes and polysiloxanes.

1 6. The copper solution of claim 15 where the silicon compound is apolysiloxane.

17. The copper solution of claim 10 where the silicon compound is addedto the copper solution by dissolution in a solvent and addition of thesolution to the copper solution.

18. The copper solution of claim 9 where the hydrogen inclusionretarding agent is an alkali metal cyanide.

19. The copper solution of claim 18 where the alkali metal cyanidecompound is sodium cyanide

2. The copper plating solution of claim 1 containing as an additionaladditive at least one member selected from the group consisting of aformaldehyde addition agent in an amount of at least 0.1 moles per moleof formaldehyde in solution to that amount that prevents deposition ofcopper and a salt of a Group VIII metal of the Periodic Chart of theElements in an amount of at least five parts per million parts ofsolution, said Group VIII metal salt having an anion noninterfering withsaid solution.
 3. In an aqueous electroless copper plating solutioncomprising a source of cupric ions, hydroxyl radicals, formaldehyde andsufficient complexing agent to render said cupric ions soluble inalkaline solution, the improvement comprising an additive in thesolution of an organic silicon compound, a solution-soluble alkali metalcyanide compound, and at least one of a formaldehyde addition agentselected from the group of alkali metal sulfites, bisulfites andphosphites and solution soluble salts of a Group VIII metal selectedfrom the group of iron, nickel and platinum, said salts of a Group VIIImetal having an anion noninterfering with said electroless coppersolution, said organic silicon compound and said alkali metal cyanidebeing present in solution in combined amount insufficient to preventcopper deposition, each of said organic silicon compound and said alkalimetal cyanide being present in solution in an amount of at least onepart per million parts of solution, said formaldehyde addition agentbeing in an amount of about 0.1 moles per mole of formaldehyde to thatamount that prevents copper deposition and said Group VIII metal saltbeing present in an amount of at least five parts per million parts ofsolution.
 4. The copper plating solution of claim 3 having as additivesthe silicon compound, the cyanide compound, the formaldehyde additionagent and the Group VIII metal salt.
 5. The copper solution of claim 4where the silicon compound is a silicone fluid.
 6. The copper solutionof claim 5 where the Group VIII metal salt is selected from the groupconsisting of NiSO4, Fe2(SO4)3 and H2PtCl6.
 7. The copper solution ofclaim 3 where the formaldehyde addition agent is selected from the groupconsisting of Na2SO3, NaHSO3 and Na2HPO3.5H2O.
 8. The copper solution ofclaim 5 where the cyanide compound is sodium cyanide.
 9. In an aqueouselectroless copper plAting solution comprising a source of cupric ions,hydroxyl radicals, a source of formaldehyde and sufficient complexingagent to render said cupric ions soluble in alkaline solution, theimprovement comprising an additive in the solution of a combination ofan organic silicon compound and a hydrogen inclusion retarding agentselected from the group consisting of a water soluble cyanide compound,vanadium, molybdenum, niobium, tungsten, rhenium, arsenic, antimony,bismuth, rare earths of the actinum series, rare earths of the lanthanumseries and mixtures of the foregoing, said organic silicon compound andsaid hydrogen inclusion retarding agent being present in a combinedamount insufficient to prevent copper deposition and said organicsilicon compound and said hydrogen inclusion retarding agent beingpresent in solution in an amount of at least 1part per million parts ofsolution.
 10. The copper plating solution of claim 9 containing as anadditional additive at least one member selected from the groupconsisting of a formaldehyde addition agent in an amount of at least 0.1moles per mole of formaldehyde in solution to that amount that preventscopper deposition and a salt of a Group VIII metal of the Periodic Chartof the Elements in an amount of at least five parts per million parts ofsolution, said formaldehyde addition agent being selected from the groupconsisting of metal salts of a member selected from the group consistingof sulfites, bisulfites and phosphites, and said salt of a Group VIIImetal being selected from the group consisting of salts of platnium,iron and nickel and having an anion noninterfering with said electrolesscopper plating solution.
 11. The copper solution of claim 10 having asadditives, the silicon compound, the hydrogen inclusion retarding agentand the formaldehyde addition agent.
 12. The copper solution of claim 10having as additives, the silicon compound, the hydrogen inclusionretarding agent and the Group VIII metal salt.
 13. The copper solutionof claim 10 having as additives, the silicon compound, the hydrogeninclusion retarding agent, the formaldehyde addition agent and the GroupVIII metal salt.
 14. The copper solution of claim 13 having thefollowing formulation: copper salt 0.02 to 0.12 moles formaldehyde 0.1to 1 moles complexing agent 1 to 3 times the moles of cupric ion freehydroxide 0.1 to 0.8 moles hydrogen inclusion 5 to 250 p.p.m. retardingagent silicon compound 5 to 250 p.p.m. formaldehyde addition 0.1 to 1times the moles of agent formaldehyde Group VIII metal salt 30 to 1,000p.p.m. Water to 1 liter of solution
 15. The copper solution of claim 10where the organic-silicon compound is selected from the group consistingof silanes and polysiloxanes.
 16. The copper solution of claim 15 wherethe silicon compound is a polysiloxane.
 17. The copper solution of claim10 where the silicon compound is added to the copper solution bydissolution in a solvent and addition of the solution to the coppersolution.
 18. The copper solution of claim 9 where the hydrogeninclusion retarding agent is an alkali metal cyanide.
 19. The coppersolution of claim 18 where the alkali metal cyanide compound is sodiumcyanide.